This paper reports the findings of a study that explored which characteristics of electronic textbooks correlated with knowledge acquisition by learners of different achievement levels. The study was carried out on 35 units of electronic textbooks that were studied by 19 high-achieving and 19 low-achieving students in four Estonian schools. The low-achieving students profited from clear instructions, familiar icons, examples, and answering from the keyboard. The high-achieving students benefited from key-combinations, menus with different levels, the Internet, analogies and lower density of terms in the content of the material. In electronic textbooks, not only the content, but also the design of the software, should be different for learners with a different achievement level.